The invention relates to materials and devices for use with electromagnetic fields and relates in particular to materials and devices through which electromagnetic fields may propagate in unconventional ways. The ability of such devices to propagate electromagnetic fields in unconventional ways permits the materials to be used for a variety of known and yet unknown applications.
For example, U.S. Published Patent Application No. 2001/0038325 discloses a left-handed composite media for use at microwave frequencies in which negative effective electrical permittivity and negative effective magnetic permeability are simultaneously provided. Such materials with negative effective electrical and magnetic permeability are disclosed to be suitable for use as microwave lenses, beam steering elements, and prisms.
A negative index of refraction for incident radiation at the frequency of light has been demonstrated using photonic crystals in Superprism Phenomena in Photonic Crystals, by H. Kosaka, T. Kawashime, A. Tomita, M. Notomi, T. Tamamura, T. Sato and S. Kawakami, PHYSICAL REVIEW B, vol. 58, No. 16 (October 1998). Such materials are disclosed to provide a propagation beam swing of ±90 degrees responsive to a ±12 degrees shift in the angle of incident radiation by modifying the group velocity of the incident radiation. A negative index of refraction has also been demonstrated in the vicinity of the photonic band gap in Theory of Light Propagation in Strongly Modulated Photonic Crystals: Refractionlike Behavior in the Vicinity of the Photonic Band Gap, by M. Notomi, PHYSICAL REVIEW B, vol. 62, No. 16 (October 2000). In particular, this article discloses that negative refraction is possible in regimes of negative group velocity and negative effective index above the first photonic band near the Brillouin zone center (Γ).
Other types of devices have been disclosed to be suitable for propagating light in one direction only. For example, U.S. Published Patent Application No. 2002/0162988 discloses a unidirectional gyrotropic photonic crystal that is disclosed to permit electromagnetic wave propagation of a certain frequency in one direction while impeding the electromagnetic wave propagation in the opposite direction.
Certain further materials are known to affect the circular polarization and amplitude of light. For example, U.S. Pat. No. 6,411,635 discloses a composite for use in selective single-mode lasing that includes a doped chiral medium. The selection is disclosed to be accomplished by producing an appropriate spatial gain distribution inside the chiral laser medium. U.S. Pat. No. 6,396,859 discloses a chiral structure that includes a defect in the form of a twist, and is disclosed to be used for filters, lasers and detectors. International PCT Publication WO 02/073247 discloses chiral substrate that is formed as a fiber to provide a fiber Bragg grating.
There continues to be a need however, for further materials and devices that provide unconventional electromagnetic field propagation characteristics, such as for example, slowing down light in one direction only, and that may provide directionality characteristics in two or three dimensions.